Electron Spin Resonance Lineshape Analysis Research Articles

Resolving Complex Photoconductivity of Perovskite and Organic Semiconductor Films Using Phase-Sensitive Microwave Interferometry

Complex transient photoconductivity (Δσ) contains rich fingerprints of charge recombination dynamics in photoactive films. However, a direct measure of both real (Δσ′) and imaginary (Δσ″) components has proven difficult using conventional cavity-based time-resolved microwave conductivity approaches. Here, we present a novel approach to resolve Δσ′ and Δσ″ parts of Δσ by using a nonresonant coplanar transmission line and a microwave interferometric detection scheme. The use of a phase-sensitive microwave interferometer greatly increases the measurement sensitivity and eliminates the requirement of a resonant cavity. This broadband detection scheme allows for direct measurement of Δσ. The relationship between the experimental phase shift and Δσ′ and Δσ″ components is decoded through an in situ electron spin resonance (ESR) measurement. ESR line shape analysis is used to confirm the assignment of the transients to the Δσ′ and Δσ″ components. We demonstrate the utility of this technique on thin films of poly(3-hexylthiophene): [6,6]-phenylC61-butyric acid methyl ester (P3HT:PCBM) and perovskite MA0.85FA0.15PbI3 films on glass.

High Frequency Electron Spin Resonance in Mn1-xFexSi

High frequency (60 GHz) electron spin resonance (ESR) has been studied for the quantum critical system Mn1−xFexSi (0 < x < 0.24) at temperatures up to 50 K by using the original experimental technique. The analysis of ESR line shape allowed detecting the full set of spectroscopic parameters (oscillating magnetization, line width and g factor). The violation of classical Korringa-type relaxation and scaling behavior of the ESR line width was found to a result from iron doping. Non-Fermi-liquid effects in the temperature dependence of the ESR line width observed at quantum critical points x* = 0.11 and xc = 0.24 are shown to be described quantitatively in the theory by Wölfle and Abrahams.

ESR Studies of Paramagnetic Centers in Pharmaceutical Materials - Cefaclor and Clarithromycin as an Example

Electron spin resonance (ESR) studies of two antibiotics, Cefaclor and Clarithromycin, have been performed in order to investigate concentration and dynamics of free radicals generated in these compounds due to thermal sterilization. For Cefaclor three combinations of temperature and heating time have been applied: 160◦C, 170 ◦C, 180 ◦C for 120 min, 60 min, and 30 min, respectively, according to the pharmaceutical sterilization norm. Clarithromycin has been heated at 160 ◦C for 120 min. The ESR lineshape has been investigated versus microwave power ranging from 2.2 mW to 70 mW. Electron spin spin relaxation time has been estimated from the ESR lineshape analysis. Concentrations of radicals generated due to di erent sterilization procedures have been compared with the purpose to select the best sterilization scheme.

Electron spin resonance investigation of the effects of methanol on microscopic viscosity, ordering, and polarity in different phases of ionomer membranes with sulfonated polyarylene backbones

Membranes constituted from sulfonated poly (arylene ether sulfone) (SPES) and sulfonated poly(ether ether ketone) (SPEEK) are characterized using electron spin resonance (ESR) to monitor the local environment of the TEMPONE spin probe (2,2,6,6-tetramethyl-4-piperidone N-oxide). The probe occupies two phases of very different polarities and mobilities in both the swollen SPES and SPEEK membranes. ESR lineshape analysis allows the individual phases to be characterized in terms of their microviscosity, local polarity, and solvent ordering. The effects of sulfonation and methanol on the individual phase properties were studied by equilibrating different membranes with water–methanol mixtures over the full range of compositions. At sulfonation levels below 50%, SPES and SPEEK membranes have numerous but smaller, elongated hydrophilic domains in which lead to restricted motion and partial ordering of the probes in comparison with Nafion. The less polar phase of the aromatic polymers is attributed to a probe population associated with the polymer backbone. Methanol penetrates this region and disrupts the backbone structure at a concentration that depends upon the level of sulfonation.

ESR probing of quantum critical phenomena in doped S = 1/2 AF quantum spin chain

The results of high-frequency (60–315 GHz) electron spin resonance (ESR) studies of CuGeO3 single crystals containing 0.9% Mn impurity are reported. The quantitative ESR line shape analysis shows that the low-temperature (T < 40 K) magnetic susceptibility of Cu2+ chains diverges as χ ∼ 1/Tα with the critical exponent α = 0.81±0.03 and therefore indicates the onset of a quantum critical (QC) regime. A scenario in which the disorder caused by the Mn impurity in quantum spin chains of CuGeO3 may lead to the coexistence of the quantum critical regime and the spin-Peierls dimerization is discussed. For the quantitative description of the temperature dependences of the line width and g-factor, a model assuming a crossover from the high-temperature semiclassical Nagata and Tazuke limit to the low-temperature quantum case described by Oshikawa and Affleck’s theory is suggested.

Quantum critical behavior induced by Mn impurity in CuGeO 3

The results of high frequency (60–315 GHz) studies of the electron spin resonance (ESR) in CuGeO 3 single crystals containing 0.9% of the Mn impurity are reported. The quantitative ESR line shape analysis shows that the low-temperature ( T<40 K) magnetic susceptibility of Cu 2+ chains diverges as χ∼1/ T α with the critical exponent α = 0.81 ± 0.03 and therefore indicates an onset of a quantum critical (QC) regime. The scenario, in which disorder caused by the Mn impurity in quantum spin chains in CuGeO 3 may lead to the co-existence of the QC regime and the spin-Peierls dimerisation, is discussed.

Association of sugar-based carboranes with cationic liposomes: an electron spin resonance and light scattering study

The possibility of cationic (di-oleoyltrimethylammonium propane, DOTAP)/( l-α-dioleoylphosphatidyl-ethanolamine, DOPE) liposomes to act as carriers of boronated compounds such as 1,2-dicarba- closo-dodecaboran(12)-1-ylmethyl](β- d-galactopyranosyl)-(1→4)-β- d-glucopyranoside and 1,2-di-(β- d-gluco-pyranosyl-ox)methyl-1,2-dicarba- closo-dodeca-borane(12) has been investigated by Electron Spin Resonance (ESR) of n-doxyl stearic acids ( n-DSA) and Quasi-Elastic Light Scattering (QELS). Both these carboranes have potential use in Boron Neutron Capture Therapy (BNCT), which is a targeted therapy for the treatment of radiation resistant tumors. They were shown to give aggregation both in plain water and in saline solution. Carborane aggregates were, however, disrupted when DOTAP/DOPE liposome solutions were used as dispersing agents. The computer analysis of the ESR spectra from carborane-loaded liposomes allowed to establish an increase of the order degree in the liposome bilayer with increasing carborane concentration, together with a decreased mobility. The same discontinuities of both correlation time and order parameter with respect to temperature variations were observed in carborane-containing and carborane-free liposomes. This suggested that a homogeneous dispersion of nitroxides and carboranes occurred in the liposome bilayer. The ESR line shape analysis proved that no dramatic changes were induced in the liposome environment by carborane insertion. QELS data showed that the overall liposome structure was preserved, with a slight decrease in the mean hydrodynamic radius and increase in polydispersity caused by the guest molecules.

Association of sugar-based carboranes with cationic liposomes: an electron spin resonance and light scattering study

The possibility of cationic (di-oleoyltrimethylammonium propane, DOTAP)/( l -α-dioleoylphosphatidyl-ethanolamine, DOPE) liposomes to act as carriers of boronated compounds such as 1,2-dicarba- closo -dodecaboran(12)-1-ylmethyl](β- d -galactopyranosyl)-(1→4)-β- d -glucopyranoside and 1,2-di-(β- d -gluco-pyranosyl-ox)methyl-1,2-dicarba- closo -dodeca-borane(12) has been investigated by Electron Spin Resonance (ESR) of n -doxyl stearic acids ( n -DSA) and Quasi-Elastic Light Scattering (QELS). Both these carboranes have potential use in Boron Neutron Capture Therapy (BNCT), which is a targeted therapy for the treatment of radiation resistant tumors. They were shown to give aggregation both in plain water and in saline solution. Carborane aggregates were, however, disrupted when DOTAP/DOPE liposome solutions were used as dispersing agents. The computer analysis of the ESR spectra from carborane-loaded liposomes allowed to establish an increase of the order degree in the liposome bilayer with increasing carborane concentration, together with a decreased mobility. The same discontinuities of both correlation time and order parameter with respect to temperature variations were observed in carborane-containing and carborane-free liposomes. This suggested that a homogeneous dispersion of nitroxides and carboranes occurred in the liposome bilayer. The ESR line shape analysis proved that no dramatic changes were induced in the liposome environment by carborane insertion. QELS data showed that the overall liposome structure was preserved, with a slight decrease in the mean hydrodynamic radius and increase in polydispersity caused by the guest molecules.

Direct Numerical Analysis of ESR Line Shape in Low Dimensional Spin Systems

We have developed a numerical method to estimate the behavior of electron spin resonance (ESR) absorption. By this method we investigated the dependence of the ESR line shape in various configurations of the external parameters in quantum spin systems with short range correlation. We found the dependence of the line shape on the temperature and also on the directions of the field. We propose to use ESR as the method to investigate the details of the geometrical and the magnetic structure of material.

Electron spin resonance line-shape analysis of x-doxylstearic acid spin probes in dihexadecyl phosphate vesicles and effects of cholesterol addition

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectron spin resonance line-shape analysis of x-doxylstearic acid spin probes in dihexadecyl phosphate vesicles and effects of cholesterol additionPeter J. Bratt and Larry KevanCite this: J. Phys. Chem. 1993, 97, 28, 7371–7374Publication Date (Print):July 1, 1993Publication History Published online1 May 2002Published inissue 1 July 1993https://doi.org/10.1021/j100130a041RIGHTS & PERMISSIONSArticle Views83Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (477 KB) Get e-Alerts

Electron spin resonance and electron-spin-echo study of oriented multilayers of L alpha-dipalmitoylphosphatidylcholine water systems

A detailed electron spin resonance (ESR) study of spin-labeled-oriented multilayers of L alpha-dipalmitoylphosphatidylcholine (DPPC) water systems for low water content (2-10% by weight) is reported with the purpose of characterizing the dynamical and structural properties of model membrane systems. Emphasis is placed on the value of combining such experiments with detailed simulations based on current slow-motional theories. Information is obtained regarding ordering and anisotropic rotational diffusion rates via ESR lineshape analysis over the entire motional range, from the fast motional region through the moderately slow and slow to the rigid limit. This includes the low-temperature gel phase, the liquid crystalline L alpha (1) phase and what appears to be a third high-temperature phase above the L alpha phase. Cholestane (CSL) and spin-labeled DPPC (5-PC, 8-PC, and 16-PC) have been used to probe different depths of the bilayer. While CSL and 5-PC both reflect the high ordering of the bilayer close to the lipid-water interface, CSL appears to be located close enough to the water for the nitroxide to be involved in hydrogen bonding with water molecules. 16-PC reflects the relatively low ordering near the tail of the hydrocarbon chain in the bilayer. Quantitative estimates of ordering and motion are obtained for these cases. The results from CSL indicate that close to the lipid-water interface the DPPC molecule is oriented approximately perpendicular to the bilayer in these low water-content systems. However, all three labeled lipid probes indicate that the hydrocarbon chain of DPPC may be bent away from the bilayer normal by as much as 30 degrees and this evidence is stronger at low temperatures. When cholesterol is added to the DPPC-water system at a concentration greater than or equal to 2.5 mol %, the ordering is greatly increased although the rotational diffusion rate remains almost unaffected in the gel phase. Electron spin echoes (ESE) are observed for the first time from oriented lipid-water multilayers. Results obtained from cw ESR lineshape analysis are correlated with data from ESE experiments, which give a more direct measurement of relaxation times. These results indicate that for detection of very slow motions (close to the rigid limit) ESE experiments are more sensitive to dynamics than continuous wave ESR for which inhomogeneous broadening becomes a major problem.

Flexibility of end-labeled polymers from electron spin resonance line-shape analysis: 3' terminus of transfer ribonucleic acid and 5S ribonucleic acid

Saccharomyces cerevisiae tRNA and 5S RNA, Escherichia coli 5S RNA, and wheat germ 5S RNA have each been specifically spin-labeled at the 3'-terminal ribose to give morpholino-spin-labeled (MSL) RNAs. Enzymatic hydrolysis with pancreatic RNase, followed by anion-exchange chromatography, confirms the site of attachment of the spin-label. Effective rotational correlation times, TB and TC, have been determined from electron spin resonance (ESR) peak heights and widths as a function of temperature for each MSL RNA, and Arrhenius plots of -log T vs. 1/T have been constructed. TC is a measure of internal flexibility at the link between the label and the RNA, while TB is a measure of rotational flexibility of the RNA near the labeled site. Validity of the TB and TC determination has been confirmed from simulation of the experimental EPR spectra by theoretical spectra computed for various attachment geometries and motional rates. Discontinuities in the slope of Arrhenius plots for TB were seen at 34 and 66 degrees C (yeast MSL tRNA), 37 and 60 degrees C (E. coli MSL 5S RNA), 37 and 57 degrees C (yeast MSL 5S RNA), and 36 and 54 degrees C (wheat germ MSL 5S RNA). Temperature-induced hydrolysis of each MSL RNA was less than 5% as determined by gel-filtration chromatography. The melting curves are consistent with a recently proposed universal secondary structural model for prokaryotic and eukaryotic 5S RNA.

Geometrical structure of solvated electrons

Recent developments in electron magnetic resonance for measuring very weak hyperfine interactions in disordered solids have made possible the determination of the detailed geometrical structure of solvated electrons in glassy matrices of varying polarity. These developments include second moment electron spin resonance lineshape analysis in selectively deuterated solvents, analysis of both the intensity and energy separation of allowed and forbidden spin-flip transitions and analysis of electron spin-echo modulation patterns. Detailed solvated electron geometries in water, methanol, ethanol, methyltetrahydrofuran and 3-methylpentane matrices are given. The dominant interactions controlling solvated electron geometry as a function of the polarity and size of the solvent molecules are elucidated.

ESR study of free and immobilized elastase

Porcine pancreatic elastase (EC 3.4.21.11) has been immobilized on polyacrylamide beads using glutaraldehyde ad bridging reagen without important loss of catalytic activity. A nitroxide spin label, 1-oxyl-2,2,5,5,-tetramethyl-4-piperidinyl-ethylphosphonofluoridate, reacting covalently with the serine-195 residue of the active centre of free elastase was used as a conformational and dynamical electron spin resonance probe. This signal is quenched by (Cu 2+) which bind specifically at the active site at a distance of 7 Å from the nitroxide group. This distance is not significantly affected by the fixation on the solid support. The electron spin resonance lineshape analysis indicates some mobility of the spin label with respect to the native protein. This restricted motion, which is pH dependent, is not noticeably modified by the immobilization of the enzyme. This immobilization has therefore induced no large conformational change of the protein in the vicinity of the active centre. Thermal denaturation of elastase in homogeneous solution is irreversible. Immobilization on the polyacrylamide beads results in 70% reversibility, but the temperature of denaturation is not modified.

Electron spin resonance line-shape analysis for determination of unresolved metal hyperfine splittings in ion pairs. Application to the benzene anion radical

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectron spin resonance line-shape analysis for determination of unresolved metal hyperfine splittings in ion pairs. Application to the benzene anion radicalM. T. Jones, M. Komarynsky, and R. D. RataiczakCite this: J. Phys. Chem. 1971, 75, 18, 2769–2773Publication Date (Print):September 1, 1971Publication History Published online1 May 2002Published inissue 1 September 1971https://doi.org/10.1021/j100687a011RIGHTS & PERMISSIONSArticle Views46Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (462 KB) Get e-Alerts